Manufacture of alkanoic acids



Patented F eb. 27, 1945 Pics MANUFACTURE O1 ALKANO IC ACIDS Louis Schmerling, Riverside, 11]., assignor to Universal Oil Products Company, Chicago, Ill a corporation ot-Delaware No Drawing. Application November 9, 1942, Serial N0. 465,096

5 Claims.

The present invention is concerned with a process for-thesynthesis of acids having ageneral structure R'P-COOH in which R represents a saturated alkyl radical.

The invention is more specifically concerned with-a new type of process in which isoparaillnic hydrocarbons are reacted with unsaturated' aliphatic carboxylic acids to form saturated allryl carboxylic acids of higher molecular weight.

In one specific embodiment the' present invention comprises a process for the manufactureof saturated alkyi mono-carboxylic acids which comprises interacting isoparafiin hydrocarbons and unsaturated aliphatic carboxylic acids in the presence of catalysts of the Friedel-brafts type.

The present process involves a new reaction which may be looked upon, from one viewpoint, as an aikylation of isoparaflin hydrocarbons with alkenyl carboxylic acids. This group of acids includes those tabulated below:

Acid Formula Meltin Boiling point, point,G.

Acrylic .CHFCHCOOH 7 140 Crotonic cHacn=cHcooH 72 182 Isocrotonic CH1=CHCH2COOH 112 Ang lic CHiCH=C-COOH 45 186 H Tlglic.. Capone-coon e5- 3 19s I (3H3 I In accordance with the present invention reaction is brought about between isoparalllns and acids of the above character or, alternatively,

their esters. I

The isoparaflin hydrocarbons include a large group, the simplest member of which is isobatane, the number of ible isomers increasing rapidly with molecular weight in the series and including such compounds as isopentane, isohexanes such as methyl pentanes and dimethylbutones, and a large number or ischeptanes including methyl hexanes, dimethylpentanes, and the compound, 2,2,3-trimethylbutane. The reactivity of these hydrocarbons with the unsatu rated carboxylic acids apparently depends upon the presence of tertiary carbon atoms.

The reactions involved in the present process are typified by that occurring between isobutane and acrylic acid to yield various heptanoic acids, these acids being formed by the interactloii of the lowest molecular'weight -representatives of the two groups of compounds which are reacted 5 between these two compounds is shown in, the- 1y room temperature up to C. may be employed when good yields are obtained. High following equation in which structural formulas are used:

a. v, C I I, Y mc-o-H' cm=oncoon 1 Acrylic acid Isobutane.

' CHs---CH2-CHEC O OH H: s 2,2'dimeth y1valcric' acid The formula on the right hand sideoi the above equation may represent a possible reaction product although this particular compound was not isolated from the mixture of isoheptanoic' acids. 7

The principal reactions involved are those in which the unsaturated acid adds to the tertiary carbon atom but other reactions are possible particularly in the case of the higher molecular weight unsaturated acids in which the double bond is present in various positions.

The reactions of the present process are pref-, erably brought about in the presence of the more reactive Friedel-Crafts type catalysts such as, for example, aluminum chloride, aluminum bromide, zinc chloride, ferric chloride, zirconium chloride, boron fluoride, etc. Reactions in the presence of halides. The temperature and pressure conditions most favorable to the production oi the desired iso-alkanoic acids will vary with the reactants and the particular catalysts employed but, in general, temperatures from approximateyields of the desired alkanoic acids are favored by relatively high ratios of isoparaffln to unsaturated acid and by the use 01' considerable amounts or metal halide catalyst in relation to the amount-oi unsaturated acid.

Batch operations may be conducted by chargin: proportioned amounts or isobaraffin, unsat urated acid, metal halide catalystand hydrogen these halide catalysts are usually accelerated by the presence of minor amounts of hydrogen optimum temperatureidetermined by'trlal while I the pressure is allowed to rise to any point which corresponds to the best temperature found for the reaction. After the reaction has ceased, the

pressure vessel is cooled and may be vented to remove light gaseous products and the contents of the vessel separated into a layer of spent cat- I alyst and products which are then further separated by fractionation or the employment of individual reactions characteristic of the compounds formed. separated unreacted substances may be recovered, reproportioned and further re- 4 acted; i I

Continuous operations may be practiced by passing proportioned mixtures of isoparailln; un-

saturated acid'and a hydrogen halide through a bed of granular metal halide at selected temperature, pressure and flow conditions with subsequent continuous fractionation and recovery of the desired products and'recycling of unreacted materials. It is within the scope of the present invention to employ supported metal halide catalystsin such operations such as, for example, prepared composites which have been produced by addingaluminum chloride to such granular 'materials as activated carbons, bauxites, and

various other refractory materials of a siliceous or oxide character. The temperatures employed in continuous operations may be higher and the times of contact somewhat lower than the conditions employed in batch operation to produce I the same results. Obvious1y,-,in commercial operations where capacities are of primary consideration, the continuous method of operation will be preferred. I s

- The compounds formed by the interaction of isoparaflins and unsaturated acids by the present process are useful in themselves in many waysand also as intermediate compounds in the prepa ration of other synthetic products. For example,

-'.they may be used as starting materials for the production of corresponding ketones and esters having particular properties and may be converted to hydrocarbons by removal of carbon dioxide by heating with alkaline earth metal hydroxides. In short, they are capable of undergoing any of the known reactions ofmono-carboxylic acids to form derivatives.

,The following example is given to illustrate the results obtainable in one particular instance involving the interaction 01' an'isoparaffin and an unsaturated carboxylic acid. However, the data are more o'r'less specific and it is .not intended that the example thus introduced should act to correspondingly limit the proper scopeof the en n- Mixtures of crotonic acid, isobutane and aluminum chloride were added to a glass-lined pressure vessel,.and a minor amount of hydrogen chloride was added. .Thevessel was then? heated I 9,870,494 halide to a pressure vessel and heating to an.

From the analysis of the products from run No. 1, it was indicated that the temperature was too low for extensive reactions to occur. The products from run No. 2 were treated with water to separate metal halide and leave an oily upper layer. The upper layer was shaken out with 'ether, washed further with water and extracted with dilute caustic soda to form alkali metal salts of the acids formed. Evaporation of the residual ether yielded 4.5 parts by weight of the product which consisted of a mixture of ketones and esters of the acids. The acidification of the alkaline extract yielded a mixture of octanoic acids boiling within the range of 205 -215 C. and having a molecular weight of 150. The octanoic acids were identified by carbon-hydrogen analyses and their boiling range indicated that they were of an iso' character since the boiling point of normal octanoic acid (caprylic acid) is 285 C.

I claim as my invention:

l. A process for the manufacture of alkanoic acids which comprises interacting an -isoparaflln hydrocarbon and an unsaturated aliphatic car'- boxylic acid in the presence of a catalyst of the Friedel-Crafts type.

at different temperatures for periods of several hours and products separated and identified. The following tabulation shows the significant data obtained in two runs:-

'2. A process for the manufacture of alk'anoic acids which comprises interacting an isoparaffin hydrocarbon and an unsaturated aliphatic carboxylic acidinthe presence of a metal halidehydrogen halide catalyst of the Friedel-Crafts type.

'3'. A process for the manufacture of alkan oic acids which comprises interacting an isoparamn hydrocarbon and an unsaturated aliphatic carboxylic acid in the presence of aluminum chloride and hydrogen chloride.

4. A-process for the manufacture of alkanoic acids comprising a substantial proportion of isoheptanoic acids'which comprises interacting isobutane and acrylic acid in the presence of a metal halide-hydrogen halide catalyst .of the Fr'iedel-Crafts type. I J

5. A process for. the manufacture of alkanoic acids comprising a substantial proportion of isooctanoic acids which comprises interacting isobutane and a crotonic acid in the presence of a metal halide-hydrogen halide catalyst of the Friedel-Crafts type.

LOUIS S CHMERLING. 

